As shown in FIG. 1, a system 1 comprises at least one digital-to-analog converter 2 receiving a baseband digital signal S as an input, an RF (Radio Frequency) mixer 3 which converts the signal to a radio frequency L0, a variable gain amplifier 4, a power amplifier 5, and a transmitting antenna 6.
There is a desire to further increase the integration of the integrated circuits comprising such systems, in order to reduce their manufacturing costs.
For example, U.S. Patent Application Publication No. 2005/0111573 proposes a technique for combining the digital-to-analog conversion and the mixer functions within the same circuit. This circuit comprises a plurality of parallel Gilbert cells. Each cell comprises three serial stages: the first stage comprises a current source, the second stage provides signals from a local oscillator for modulating the currents of the third stage, and the third stage provides currents as a function of the value of a baseband signal.